readLabels method
Reads label data for a rectangular area defined by two corner tiles.
Default implementations typically combine results from individual tiles, which may be inefficient for large areas.
Precondition: upperLeft.tileX <= lowerRight.tileX && upperLeft.tileY <= lowerRight.tileY
upperLeft Upper-left corner tile of the requested area
lowerRight Lower-right corner tile of the requested area
Returns combined label data for the area
Implementation
@override
Future<DatastoreBundle> readLabels(Tile upperLeft, Tile lowerRight) {
// TODO: implement readLabels
throw UnimplementedError();
}